1. Field of the Invention
This invention relates to a radiation image recording and reproducing system for once recording a radiation image on a stimulable phosphor sheet, scanning the stimulable phosphor sheet with a stimulating ray which causes it to emit light in the pattern of the radiation image stored therein, reading out and converting the emitted light to an electric signal, and then reproducing a visible image by use of the electric signal. More particularly, this invention relates to a radiation image recording and reproducing system in which a particular stimulable phosphor sheet can be sent to an image read-out section in preference to another phosphor sheet and the radiation image stored on said particular phosphor sheet can preferentially be reproduced to a visible image.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to such radiation as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to a stimulating ray such as visible ray, light is emitted from the phosphor in the pattern of the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264 and 4,276,473, 4,346,295 and 4,387,428, Japanese Unexamined Patent Publication No. 56(1981- )11395, it has been proposed to use the stimulable phosphor for recording a radiation image. Specifically, the stimulable phosphor is first exposed to a radiation to have a radiation image stored therein, and is then scanned with a stimulating ray which causes it to emit light in the pattern of the stored image. The light emitted from the stimulable phosphor upon stimulation thereof is photoelectrically detected and converted to an electric image signal, which is processed as desired to reproduce an image of a quality suitable for viewing and diagnostic purposes. The image finally obtained may be reproduced as a hard copy or on a cathode ray tube (CRT).
When the radiation image recording and reproducing method described above is practically used for medical diagnosis, the stimulable phosphor sheet provided with a stimulable phosphor layer is used, in general, in the form in which it is held in a case such as a cassette for containing a stimulable phosphor sheet or a magazine for containing several phosphor sheets. In hospitals and the like, since a great number of images must be processed quickly, it is preferable to use a sheet feeder for receiving the case containing a stimulable phosphor sheet or sheets, automatically taking up each sheet from the case and sending it to a line for feeding it to an image read-out section, or to use an image input table or stand provided therein with such a sheet supplying mechanism.
In many large hospitals and the like, it is necessary to use a plurality of image input stands respectively designed for recording a radiation image by use of the cassette or the magazine. Further it is practicable that each image input stand can work with stimulable phosphor sheets of several different sizes according to the portions of an object to be recorded. Therefore, a plurality of sheet feeders will also be used according to the kinds of the image input stands and the sizes of the stimulable phosphor sheets.
In order to put the above-mentioned radiation image recording and reproducing method into practice in hospitals, a stacker for temporarily storing the stimulable phorphor sheets sent from the image input section and sequentially feeding the sheets one by one to the image read-out section must be used unless the processing capacity in the image read-out section and the subsequent sections is always equal to or larger than the number of stimulable phosphor sheets sent from the image input stands. The stacker is required particularly when only one image read-out apparatus is used for many image input stands and sheet feeders. However, the stacker is necessary also when there are many image read-out apparatuses since the processing load sometimes exceeds the capacity of the image read-out apparatus if there are a great number of patients coming to consult the radiologist at a time. This also applies when an image read-out apparatus is used for a set of the image input stand and the sheet feeder.
In hospitals, it often happens that a radiation image of a particular patient should be urgently reproduced to a visible image in preference to that of another patient. However, in the radiation image recording and reproducing system using the image input stand, the sheet feeder, and the stacker for receiving the stimulable phosphor sheets from the sheet feeding line and sequentially sending the sheets to the image read-out apparatus, even if the image input stand is preferentially used for the particular patient and the stimulable phosphor sheet carrying the radiation image of the patient is quickly sent to the sheet feeder, the phosphor sheet cannot be quickly fed from the sheet feeder to the sheet feeding line when another sheet feeder is feeding other phosphor sheets therefrom to the sheet feeding line. Further, even when the stimulable phosphor sheet carrying the radiation image to be preferentially processed is fed to the stacker via the sheet feeding line, the radiation image cannot be read out before all phosphor sheets already existing in the stack zone of the stacker have been processed in the image read-out apparatus. Thus, in the above-mentioned radiation image recording and reproducing method, it is impossible to preferentially process a particular stimulable phosphor sheet.